MTO recommends giving them 1 metre of space to your right, and if the cyclist is riding defensively, they will also be leaving themselves about 1 metre to the curb. If you can't give them that space then you should signal and change to the next lane to pass.

A lot of streets up here have no curb, so I can incorporate the gravel shoulder into the defensive 1 metre to my right. On those streets I will ride about 15 cm from the solid white line and cars have just enough room to pass me by driving to the left edge of the lane. Near a crest of a steep hill on a two-lane road I will move out and take up the entire lane to prevent cars from straying into oncoming lanes.

In downtown areas you will likely never be able to pass a cyclist properly unless you switch lanes or they have a bike lane. In Toronto though, I have noticed that there is almost an unspoken rule that cars in the left lane will shift over, allowing cars in the right lane to straddle both lanes for a bit and pass the cyclist safely. It would be a bad idea to assume this space will always open up, though.